This invention relates to an apparatus for resin-sealing a plurality of semiconductor devices, and a resin sealing method thereof.
In the conventional semiconductor apparatus of a resin-sealing type package, semiconductor devices are arranged on a read-frame, and are resin-sealed by the use of the known transfer mold method.
However, when a plurality of semiconductor devices arranged on a large wiring substrate are resin-sealed, a molding die will be required. This die is generally expensive in cost. Further, the resin-sealed package can not be thinned.
Even when the die is thinly produced, a warp or a crack takes place for the package. Further, the semiconductor device floats in a cavity by a resin injection pressure. As a result, the semiconductor device is obliquely resin-sealed. Moreover, a wiring pattern will be exposed from the package.
To solve these problems, suggestions have been made about a resin-sealing method by filling resin by the known potting method or screen printing method.
With respect to these methods, disclosure has been made about the resin-sealing method due to the screen printing method in Japanese Unexamined Patent Publication (JP-A) No. Hei. 2-251153 and Japanese Unexamined Patent Publication (JP-A) No. Hei. 11-251341.
In these methods, a single semiconductor device arranged on a film is resin-sealed. More specifically, the semiconductor device is arranged on the film fixed at the periphery thereof.
In this condition, the semiconductor device is covered with a metal mask. Further, a liquid resin is dropped for the metal mask.
In this event, a squeegee is traveled or moved on the metal mask, and the liquid resin is fallen down or dropped from the window of the metal mask.
Thereby, the liquid resin is filled in a space portion including the semiconductor device under the window of the metal mask.
Under such a circumstance, a trial has been made as follows.
Specifically, the flame is attached to the periphery of the wiring substrate, and the metal mask having a large number of small holes is arranged on the frame.
Further, the liquid resin is dropped onto the mask, and the squeegee is traveled on the mask. Moreover, the liquid resin is dropped from the holes, and the liquid resin is filled in the frame.
As a result, although a resin surface which is relatively thin can be obtained, a filling volume is large as compared with the semiconductor device arranged on the above-mentioned film, and a filling time also becomes long.
Referring to FIGS. 1A and 1B, description will be made about the conventional resin-sealing method by the use of the liquid resin so as to solve the above-mentioned problems.
A plurality of semiconductor devices 24 are arranged on a substrate 21 having a frame. The substrate 21 is provided on a stand 22, as illustrated in FIG. 1A.
With this structure, the mask (not shown) having a slightly larger opening portion than the opening portion of the substrate 21 is placed on the substrate 21, so that the opening portion of the frame is exposed.
In this condition, the liquid resin 23 is filled at a higher position than an upper surface inside the frame, and the squeegee (not shown) is traveled with a constant tilt angle on a mask plate (not shown) positioned over the frame.
As a result, the surface of the liquid resin 23 filled inside the frame is recessed or depressed in a part of the opening portion where the squeegee is initially traveled.
On the other hand, the edge of the opening portion, where the travel of the squeegee is completed, is protuberated.
As described above, when the liquid resin 23 is depressed or protuberated from the frame surface, it is unsuitable to provide a chip as the semiconductor device 24 under these portions. This is because the semiconductor or the wiring portion is exposed.
In the meantime, the protuberated portion must be removed, and as a result, unnecessary steps are also required.
Alternatively, the semiconductor device 24 may be arranged in the central portion of the substrate 21 having the frame by enlarging the substrate considering the recess or the protuberance.
However, the large substrate can not achieve the reduction in size, and inevitably consumes a large quantity of resin liquid. Consequently, this alternative method is also unsuitable.
It is therefore an object of this invention to provide a resin-sealing apparatus capable of rapidly sealing resin so as to smooth a resin surface by using a liquid resin.
According to this invention, an apparatus for sealing a resin uses a liquid resin.
A substrate has a frame for surrounding the substrate and is provided with a plurality of semiconductor devices. Herein, the substrate has a first opening portion.
A squeegee guide plate is placed on the frame and has a second opening portion. In this event, the second opening portion is larger than first opening portion in size.
A first squeegee moves along the squeegee guide plate in a first direction, and rakes the liquid resin. In this case, the liquid resin is protuberated in order to bury the semiconductor devices.
A second squeegee moves along the squeegee guide plate in a second direction opposite to the first direction, and further rakes the liquid resin so as to smooth a surface of the liquid resin.
A turning mechanism serves to turn the second squeegee in a circular arc form when the second squeegee is moving.
In this case, the turning mechanism preferably includes a squeegee head, a pair of fixing members, a linking member, a circular arc gear, and a motor.
Specifically, the squeegee head is attached to the first squeegee, and has guide grooves of a circular arc form having a pair of coaxial circles.
The fixing members slide along the guide grooves, and fix the second squeegee. The linking member links the fixing members to each other.
The circular arc gear is fixed to the fixing members. The motor rotates the gear.
The apparatus further includes a supporting portion which supports the first and second squeegees, and an up-down transferring mechanism which transfers the supporting portion upward and downward.
The apparatus further comprises an air cylinder which transfers the first squeegee forward and backward.
The apparatus further includes an angle-adjusting board which adjusts a slope of the first squeegee.
With such a structure, the first squeegee moves in the first direction along the squeegee guide plate.
The liquid resin is dropped into the frame of the substrate so as to protuberate over the semiconductor devices. The protuberated liquid resin is raked.
The second squeegee moves in the second direction along the squeegee guide plate. The liquid resin is raked again, so that a tilt angle between a liquid resin surface and the second squeegee is gradually increased by the use of the turning mechanism.